I. Field of the Invention
The present invention relates generally to fuel systems for internal combustion engines and, more particularly, to a high pressure fuel pipe construction particularly suited for a direct injection engine.
II. Description of Related Art
Many modern internal combustion engines of the type used in the automotive industry rely upon high pressure fuel injection to supply fuel to the engine. Typically, a rigid metal conduit has one end attached to the outlet from a high pressure fuel pump while the opposite end of the conduit is open to a fuel rail. Conventionally, a ball is attached to each end of the fuel conduit and this ball is received within a like shaped seat on both the fuel pump outlet as well as the fuel rail for the fuel injectors. Nuts then secure the balls to their seat at both the fuel rail as well as the fuel pump.
The previously known fuel conduits have proven adequate for many types of internal combustion engines, such as multipoint injection engines. However, modern day internal combustion engines increasingly utilize direct injection into the engine combustion chamber for increased efficiency and fuel economy. Since the fuel injector for direct injection engines must overcome the high pressures present within the internal combustion engine, the previously known fuel systems for direct injection engines require higher fuel pressure than the previously known multipoint fuel injection systems.
The fuel supply systems for direct injection engines are subjected to increased mechanical stress as contrasted with the previously known multipoint fuel injection systems. This increased mechanical stress results not only from engine vibration imparted directly to the fuel delivery system, but also high pressure pulsations from the fuel pump itself. In extreme cases, this high mechanical stress imposed upon the fuel system can cause a failure of the fuel delivery system. Such failures may result in cracks formed between the connection of the ball couplings at the ends of the fuel supply conduit.
Although thicker tubing may be used as the fuel supply conduit, such thicker tubing increases not only the cost of the fuel system, but also its weight.